A representative and minimal example of low-mass LLP reach is the singlet scalar LLP that has a tiny mixing angle \(\theta \)  with the Higgs boson, shown in Figure REF . (For details see [1]}, [2]}).
Part (b), where an exotic Higgs decay branching fraction of \(\mathrm {Br}(h \rightarrow ss) = 0.01\)  is assumed as an additional LLP production process, demonstrates the advantage gained by the high LHC energy even when searching for very light LLPs, since they can be produced in high-scale processes that are kinematically suppressed at intensity frontier experiments.
Also shown are the expected sensitivities of other proposed experiments like FASER [3]}, CODEX-b [4]}, and SHiP [5]}.
